Ailanthus Webworm Moth

red beetle with white flower-like spotsAugust 20, 2009I found this beauty on a table on my side porch. I live in the woods next to a reservoir in northern NJ. Any idea what this is?KerriBoonton, NJ

Ailanthis Webworm Moth

Hi Kerri,The caterpillar of the Ailanthus Webworm Moth, Atteva punctella eats the leaves of the dreaded Tree of Heaven, Ailanthus altissima. This noxious weed tree, a native of China, is invading native forest land from coast to coast. It has long been a fixture in cities especially in areas of urban blight where it thrives. It is the tree from A Tree Grows in Brooklyn, the novel by Betty Smith. Sadly the Ailanthus Webworm only eats the leaves of the tree and this does no lasting damage. We would live to find an insect that bores into the trunks or roots and destroys the plant. We believe the Ailanthus Tree might be the most dangerous invasive exotic plant to the native North American ecosystem. Once it becomes established, it takes over, crowding out all other species. You photo is quite beautiful.

We suspect yes as this is a native moth, but the Ailanthus is not native. BugGuide lists no other larval food plant. According to the University of Arkansas Arthropod Museum: “In their native habitats of Central and South America, Ailanthus webworm caterpillars build communal webs in native trees of the family Simaroubaceae. The species has spread north through much of the United States, where its caterpillars utilize primarily an introduced simaroub, Tree of Heaven, Ailanthus altissima. Tree of Heaven is native to North China. It was planted extensively in Europe in the 1700s and soon made its way to North America, where it is now naturalized along fences, roads, and in waste places.” According to the Butterflies and Moths of North America, Caterpillar hosts are: “Ailanthus and paradise tree.” You may read about the Paradise Tree on the Florida Native Plant Society Blog. Because the Ailanthus Webworm was able to adapt to eating an introduced tree, the range of the moth greatly increased as the Tree of Heaven has spread throughout the continental United States, and some might even say this scourge has spread across the planet.